High-frequency electromagneticwave translating element



June 13, 1950 H. A. WHEELER HIGH-FREQUENCY ELECTROMAGNETIC WAVE TRANSLATING ELEMENT 2 Sheets-Sheet 1 Filed NOV. 16, 1944 Incident Wave 'Il IIIIIIIIMIIIIIIIIJ Lominaions parallel to plone of cross section INVENTOR. HAROLD A4 WHEELER BYC/ ATTOZE June 1'3, 1950 H. A. WHEELER 2,511,610

HIGH-FREQUENCY ELECTROMAGNETIC WAVE TRANSLATING ELEMENT Filed Novq 16, 1944 .2 Sheets-Sheet 2 IN V EN TOR.

ATTO RN EAY Patented June 13, 1950 HIGH-FREQUENCY ELECTROMAGNETIC- WAVE TRANSLATING ELEMENT Harold A. Wheeler, Great Neck, N. Y., assignor, by mesne assignments, to Hazeltine Research, Inc., Chicago, Ill., a corporation of Illinois Application November 16, 1944, Serial No. 563,715

18 Claims.

The present invention relates to electromagnetic-wave translating elements and, particularly, to such elements for propagating or aiding in the propagation of high-frequency electromagnetic waves along a restricted path, which path may be linear or nonlinear as desired.

A transmission line, having two conductors supported in insulated spaced relation, is Widely used for purposes of propagating an electromagnetic wave between given spaced points. The electromagnetic wave follows, or is guided along, the conductors and travels with the speed of light if the conductors are surrounded only by air dielectric. In one form of transmission line of this nature, one of the conductors is enclosed within the other to forma shielded transmission line, whereby the propagation of the electromagnetic waves is along a restricted path enclosed by the outer conductor. A particular form of such transmission line is one having conductors of circular cross section supported in concentric relation to provide a coaxial transmission line. The extensive utility and advantages of these forms of transmission line are well known to persons skilled in the art.

In one form of transmission line of the type described, insulating spacers are positioned along the line to maintain the conductors in uniform spaced relationship and electrically insulated from each other. The spacers heretofore employed for this purpose increase the capacitance of the line in the region occupied by the spacers. This has the effect of changing the characteristic impedance of the line in this region and an electrical impedance discontinuity is thus produced on the line at each of the spacers. A point of discontinuity is said to occur when reflection of wave-signal energy occurs at that point. Discontinuities of this nature have increasingly serious effect as the frequency of the translated wave signal becomes increasingly higher since the length of each such discontinuity longitudinally of the line then becomes a larger fraction of a, wave length of the wave signal. The undesirable effect of such reflections of Wave-signal energy arises from the fact that they produce standing waves of voltage and current along the line and thus reduce the power translated to a wave-signal translating device coupled to the remote end of the line for reasons well known. To avoid the change of line impedance produced by such spacers, it has been proposed that the cross-sectional sizes of the transmission-line conductors be modified over the length of the spacers to maintain substantially constant the characteristic impedance of the line throughout its length. Alternately, it has been proposed that the spacers have a longitudinal length critically related to the frequency of the propagated wave signal in order that the wave-signal energy reflected by the two surfaces of the spacer in the path of wave-signal propagation shall have opposing phase relationships, thus to nullify the effect along the line ofthe reflected energy. This, of course, limits the usefulness of the line in that it can propagate a wave signal of only one frequency if standing waves are to be avoided.

Yet another device which effects propagation of electromagnetic waves along a closed restricted path is the so-called wave guide. A wave guide may be essentially a hollow conductor having internal dimensions critically related to the wave length of an electromagnetic wave to be propagated thereby. An electromagnetic wave of the proper wave length, once started on its way down the interior of the wave guide, will continue traveling therealong and will follow the wave guide even though the latter isnonlinear but contains gradual bends along its length. The propagation of Wave-signal energy in a straight wave guide is free of reflections and this is approximately true for any gradual bends occurring therein. v Sharp bends in the wave guide, on the other hand, are highly undesirable since they may form a severe discontinuity with consequent distortion of the electromagnetic-wave front and consequent appreciable reflection of wave-signal energy. It is frequently desirable to provide such sharp bends in wave guides, but their attendant disadvantages have heretofore greatly restricted and minimiaed their use, thus to place an undue limitation on the usefulness of wave guides in practice.

In certain applications, it is desirable that electromagnetic waves be propagated over a restricted path without boundaries, as a beam similar to a beam of light, This has been accomplished in accordance with one prior practice by the use of suitably shaped wave-signal reiiectors properly positioned with relation to an electromagnetic-wave radiating source. In addition to or in lieu of such reflectors, dielectric lens elements have been employed to facilitate focusing the electromagnetic-wave energy into a beam of desired configuration. Lens elements of this nature have heretofore been comprised simply of a dielectric material, for example polymerized styrene. operative to effect the desired focusing action, their impedance to the propagation of electro- While such lenses usually are.

magnetic waves is different from that of the freespace wave-signal propagation path immediately preceding and following the lens element with the result that undesired reflections of wave-signal energy occur at the surfaces of the lens element. This not only results in undesirable loss of wavesignal energy in the desired path, but has the additional disadvantage that such energy is propagated in many undesired directions unless additional means is employed to absorb, or otherwise to prevent, the reflected Wave-signal energy from traveling in suchimdesired directions.

In a particular form of transmission line, primarily useful for communication circuits laid under a river or under the sea', an Vinsulated conductor is enclosed in coaxial relation within a protective sheath or shield of 'conductive material and is loaded by a continuous spiral winding of iron ribbon applied directly over the inner conductor. The magnetic loading of the line in this manner is primarily for the `purpose' of increasing its characteristic impedance and thereby reducing attenuation and phase distortion over a band of frequency components 'of a very"l'oW-frequency electromagnetic wave to be propagated. The object has beento secure as high effective permeability as possible, regardless of the dielectric constant of the cable insulation, by the use of special materials such as that Sold under the trade name Permalloy It is an object of the present invention to provide a new and improved high-frequency electromagnetic-wave translating element which v'avoids one or more o'f the limitations land disadvantages of prior elements of the type'desc'ribed.

It isa vfurther object of the invention to providel anew and improved high-frequency electromagnetic-Wave translating element having high v'ehiciency of wave propagation and mini- .f

mum reflection of wave-'signal energy from the boundary surfaces thereof in the path of wavesignal propagation.

It'is an additional object of the invention to provide an imp-roved high-frequency'electromagnetic-wave translating `element which exhibits both dielectric and magnetic qualities and one which presents to a high-frequency electromagnetic wave to bepropagated thereby any desired value ofA impedance within a relatively wide range of impedance values.

It is another object of the invention vto provide a new and improved high-frequency electromagnetic-wave element having boundary surfaces in the path of wave-signal propagation of such conguration as to refract Velel's'tromagnetic waves propagated by theelement and one which may have for v`such waves any desired index of refraction, within a range of such values, while at 'the same time exhibiting'a minimum of wavesignal reflection from the vboundary Asurfaces of the element.

In accordance with'the invention, 'a high-frequency electromagnetic-'wave translating element comprises dielectric and magnetic materials 'having perceptible boundaries 'and combined'in quantities `so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal 'propagation therethrough, an effective dielectric constant and a 'substantially equal effective vmagnetic permeability.

In accordance'with onelform of'theinvention an electromagnetic-wave "translating element, adapted to be interposed in 'a wave-signal .propil agation path having a predetermined ratio of dielectric constant to magnetic permeability, comprises dielectric and magnetic materials combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal propagation therethrough,

a ratio of eiective dielectric' constant to effective magnetic permeability substantially equal to the aforesaid predetermined ratio.

The translating element of the present invention is related to the translating arrangement of applicants copending application entitled High-frequency electromagnetic-wave translating arrangement, Serial No. 563,716, iiled November 16, v1944, now Patent No. 2,508,479, granted May v23, 1950, and assigned to the same assignee as the present application. The translating arrangement of the copending application comprises a wave-signal propagating device adapted to effect propagation of high-frequency electromagnetic waves along a predetermined propagation path, of Which at least a portion has a predetermined ratio of dielectric constant to magnetic permeability', and an electromagnetic- 'wavepropagating element interposed in such portion of the path to modify the velocity of wavesignal propagation therethrough, this element including dielectric and magnetic materials combinedin quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal propagation therethrough and along the propagation path, a'ratio of eiective dielectric constant to eiective magneticl permeability for the element substantially equal to the `aforementioned ratio.

Fora better understanding ofthe present invention, together with 'other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope -will be pointed out in the appended claims.

Referring to theY drawings, Fig. 1 illustrates a high-'frequency electromagnetic-wave translating element embodying the present invention in a particular form; Fig. la illustrates a form of translating element similar to that of Fig. 1 and is used as an aid Yin explaining the proper proportioning of 'the material thereof; Fig. 2 illustrates rmodiiied forms of the invention suitable for use in a Vcoaxial transmission line; Fig. 2a represents a cross-sectional view of the Fig. 2 arrangement taken along the cross-sectional plane a-a; Figs. 3oz-3d illustrate cross-sectional views of translating elements having modied coniigurations which aresuitable for use in a coaxial ;transmission line; Fig. 4 illustrates a crosssectional view of ya form o'f wave-signal translating device embodying the invention as used in a coaxial transmission line to effect a reduction of wave-signal velocity therein, thereby eiectively to increase the electrical length of the line; Figsya and 5b illustrate top-and side views of an embodiment of the invention wherein a Wavesignal translating element is utilized as a spherical lens; Figs. 6a and 6b illustrate a top vievi1 and alongitudinal sectional view, respectively, of wave-signal translating elements of the invention utilized as cylindrical lens elements in horn type of wave-signal radiators; and Figs. '7a. and '7b illustrate wave-signal translating elements embodying the -invention as used in wave guides to 'eiect changes of direction of wave-signal energy propagated through the wave guides.

Referring now more particularly tov Fig. 1 of the drawings, there is illustrated a high-frequency electromagnetic- Wave translating element embodying the present inventionin a particular form having numeroususeful applications in a two-conductor balanced transmission line. In this ligure, the electromagnetic-wave translating element I0 is positioned between the conductors II, I2 of a balanced open-pair transmission line to maintain theconductors II, I2 in spaced relation. The inner surfaces of the conductors I I, I2 are thus arranged in spaced-opposing relation and are adapted to effect propagation, along a propagation path therebetween, of high-frequency electromagnetic waves. By the term high frequency as used in the present specification and claims is meant a frequency suiiiciently high that the maximum dimension of a given wave-signal propagation path normal to the direction of wave-signal propagation through the path is an appreciable fraction of a wave length of the propagated eletromagnetic wave. for example about l/OOO wave length or larger fraction.

i To illustrate the character and advantages of the present invention, it will be assumed that the translating element III is one of a number of similar elements spaced along the transmission line, each such element having a length longitudinally of the line which is short with relation'to the line length, and that the line otherwise uses air dielectric over the length thereof not occupied by the element Il). Since air by definition has a dielectric constant k equal to unity and a magnetic permeability it also equal to unity, the impedance of those portions of the line which use air dielectric has a value equal to w//k or unity. Any changes of characteristic impedance along the line produce impedance discontinuities therein and cause at each such point of discontinuity undesirable reflection of wavesignal energy. A dielectric material has unity relative magnetic permeability but a dielectric constant greater than unity. Hence, the use of dielectric material alone between the line conductors produces a change of line impedance, assuming no change of conductor cross section or spacing, since for a dielectric material is not equal to unity. The use of short lengths of dielectric material in a transmission line otherwise employing air as a dielectric consequently results in impedance discontinuities along the length ofthe line which may cause serious reflections of wave-signal energy when'the latter is of relatively high frequency.

In accordance with the present invention, the translating element IIJ while utilizing dielectric material nevertheless is made to have a ratio of p to Ic equal to unity. This is accomplished by forming the translating element I0 of layers or lammations alternately of dielectric material I3 and magnetic material I4, the maximum lamination thickness being much less than one radian length of the highest-frequency electromagnetic wave to be translated. The magnetic material I4 preferably. comprises particles of magnetic material, for example comminuted or powdered iron dust, dispersed or held in solid suspension in a dielectric material to provide a homogeneous magnetic material having the particles of magnetic material individually insulated from each other. The dielectric constant of the magnetic material I 4 will, of course, be higher than that of the dielectric material used therein due to the conductivity of its magnetic particles. The magnetic material I4 thus has a predetermined value of magnetic permeability and a predetermined value of dielectric constant. The dielectric material I3, on the other hand, has unity magnetic permeability and a dielectric constant greater than unity. In accordance with the invention, the dielectric and magnetic materials of the translating element I 0 are combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal propagation therethrough, an effective dielectric constant and a substantially equal effective magnetic permeability.

The required modes of wave-signal propagation for the laminated construction of Fig. 1 is indicated by the arrows associated with the figure. Thus, the direction of electromagnetic-wave propagation is parallel to the laminations of the element I0, the wave having such polarity or mode of propagation that its magnetic field is normal to its direction of propagation but parallel to the laminations of magnetic material I4, as indicated by the arrow H, While its electric eld is normal to the laminations as indicated by the arrow E.

The proportioning of the dielectric and magnetic materials of the translating element IIl will now be considered in greater detail with reference to Fig. 1al wherein the translating element III is shown as formed of a dielectric material I3 having a thickness a1 with magnetic permeability in and dielectric constant k1, and a magnetic material I4 having a thickness a2 with magnetic permeability a2 and dielectric constant k2. While the translating element IB' is shown as having only two layers of dielectric and magnetic materials, it will be understood that if desired both the dielectric and magnetic materials may be further laminated, as in Fig. 1, but that in any event the thicknesses a1 and a'z thereof are considered as representing the sum total of the thicknesses of all such laminations or layers. It can be shown that, for unity ratio of effective magnetic permeability to effective dielectric constant of the translating element I0', the thickness ai of the dielectric material is given by the following relation:

It is apparent that ai has from Equation 1 or 1A two values. For greatest accuracy of calculation, Equation 1 should be used with the positivesign before the radical for the smaller value of a1 and Equation 1A should be used with the positive sign before the radical for the larger value of a1. Values of a1 greater than unity or negative deman@ 7 note astructure whichcannotbe physically constructed. c.

The .effective dielectric constant o'f the magnetic material usually is larger than theeifectivc magnetic permeability thereof 'even though the magnetic particles of the 'material have, asA a homogeneous mass disassociated from the dielectric materiaL'high magnetic permeability. Consequently, it is usually preferable to use for .the laminations of dielectric .material one .having a relatively low dielectric constant, for example polystyrene or Lucite foam, the latter having a dielectric constant oi approximately 1.1. In fact, the iaminations of magnetic material may simply be suitably maintained in spaced relation, as by very small insulating spacers inserted therebetween7 so that the space'between the laminations of magnetic material comprises largely air dielectric, thus to reduce the dielectric constant of the substance between the magnetic laminations'to unity.

A translating element 'lil of the type described has the same characteristic impedance as free space, but propagates an electromagnetic wave with less velocity than in free space. The reductionof Wave-signal velocity effected by the translating element has utility, for example, in increasing the effective electrical length of a transmission line with which the element'is used. Oi the two values of a1 given `by Equation 1 or 1A, that which provides the thickest layer or layers of magnetic material results in the greatest reduction of wave-signal Velocity in the element lil since the effective dielectric constant and effective magnetic permeability of the element are then both large. vThe value 'of a1 which provides a thinner layer or thinner layers of magnetic material results in a larger wave-signal velocity in element l0, although this velocity is still le'ss than that of free space, due to the smaller values of effective dielectric constant and magnetic permeability of the 'eiement It will be apparent'from the foregoing description of the translating element of the present invention that, while the element is shown as'used in conjunction with conductors of -a transmission line, for very high-frequency electromagnetic waves it has utility as a so-called dielectric wave guide. Such a guide, -as is wellknown, is itself capable of propagating electromagnetic waves when the dimensions of the `guide in a cross-sectional plane normal 'to 'the Vdirection of wave-signal propagationhave values suitably'related to the frequency of the electromagnetic waves.

Fig. Zillustrates several modiiied'forms .of highfrequency electromagnetic-wave vtranslating elements suitable for use in a coaxial transmission line having an outer conductor Il and an inner conductor l2 supported in coaxial relation by a translating element embodying the vpresent invention. The translating element I" comprises concentric cylindrical layers alternately of dielectric material I3' and magnetic material i4 which surround the inner conductor l2 andiill the space between the conductors H' `and l2'. The translating element may extend along .the entire length of the transmissi-on line, as where it is desired that the transmission line be of the flexible type having an outer braided conductor I l' and an inner conductor l2 formed Yof strands of wire, or may simply be a short spacer as 'shown by vthe element Ill" which has utility in a relatively rigid transmiss'ion'line. The dielectric and magnetic materials oi a translating element of 8 the multi-layered .laminatedconcentric type, .such as the elements lll vor 1.0" ,of Fig. '2, are proportionedin .the manner Vdescribed in connection with the elements ll 4and vlil of Figs. 1 and la. An additional vform of translating element |0" shown .in Fig. 2 has a single cylindrical layer of magnetic material i4 surrounded by a single concentric layer of. dielectric material i3". In this case, the relative total thickness of the layers of dielectric .and magnetic materials as determined rby the use of Equation 1 or 1A must be modified by taking into account the fact that the potential gradient .between the inner and outer.

conductors of the transmission line varies eX ponentially between the conductors. Thus, referring to Fig. 2a, which represents :a cross section along the plane a-a of Fig. 2, if the outer conductor l lhas an inner radius r1 and the inner conductor l2 an outer radius r3, the outer radius r2 of the magnetic material I4", or the inner radius r2 of the dielectric material I3, is given by either of the following relations:

While the translating element of the present invention has heretofore been described as involving layers .or laminations of dielectric and magnetic materialsby which to maintain unity ratio of effective vmagnetic .permeability to eiective dielectric constant, it will now be apparent that the primary purpose `of the layer or layers of dielectric material is to reduce the enect of the relatively large dielectric constant of the magnetic material sumciently to attain the desired ratio of eiective magnetic permeability to eifective dielectric constant. As earlier mentioned, air gaps between the layers or laminations of magnetic material are effective for this purpose in vlieu .of intervening layers -or laminations of dielectric material. Figs. But-3d illustrate configurations of translating elements suitable for use in Va coaxial type of transmission line wherein air gaps areemployed by which to attain .the desired unity ratio of eective magnetic permeability to eifective dielectricconstant.

In Fig. 3a, the electromagnetic-wave translating element 2D is formed of a homogeneous mixture of dielectric and magnetic materials which preferably are proportioned in quantities so related to their dielectric constant and magnetic permeability as to Vprovide as close an approximation as possible to the desired ratio of magnetic permeability todielectric constant. In this proportioning, 'the'individual dielectric constants and magnetic permeabilities of the two material-s are regarded as thoseof the homogeneous materials per se. ASince the effective dielectric constant of most known magnetic materials is `high due to their conductivity, powdered iron having a dielectric constant lo'f approximately innity, .a homogeneous mixture of dielectric and magnetic materials usually has an effective dielectric constant larger than its effective magnetic permeability. To reduce the effective dielectric constant of the translating element 20 of Fig. 3a, the element is constructed with such configuration that it has a Vcentral hub portion 2| which forms la complete magnetic path of relatively low reluctance around lthe inner conductor 22 of the transmission line and'has radial arm portions 2'3 which'extend from the hub portion 2l to the outer conductor24 of the transmission line. The

radial thickness of the "length and circumferential thickness of the radial hub portion 2| and the portions 23 of the element 2U for a unit length of the latter are proportioned with relation to each 4 other and to the magnetic permeability and dielectric constant of the homogeneous mixture of materials used therein to provide the desired unity ratio of effective magnetic permeability to effective dielectric constant for the element 20. the configuration shown, it will be evident that With to effective dielectric constant for the member may readily be made unity even though the effective dielectric constant of the homogeneous mix- `ture of materials of element 2U is muchlarger than its effective magnetic permeability.

The electromagnetic-wave translating element 'L26' of Fig. 3b has such configuration that every electric line of force between the conductors 22 and 24 of the transmission line must traverse at least one air gap. Thus, the element 20 has three portions 25, 26 and 21 which provide closed paths for the magnetic field surrounding the inner conductor 22 of the line, but the radial arms 2S, 28 which connect the portions 25 and 26 of the element are normal to the radial arms 29, 29 which connect the portions 26 and 21 of the element. Consequently, the radial thicknesses of the portions 25,26 and 21 are selected to attain 'the desired unity ratio vof effective magnetic pery Yrmeability to effective dielectric constant for the element 20.Y i y Figs.3c andd illustrate configurations of the electromagnetic-wave translating element which .permitV some control over the effective radial a thickness and length of the magnetic path provided around the inner conductor` 22 of the line by the translating element. In Fig. 3c, the translating element 2U is provided with apertures 3i!v the hub portion 2| of the element 20" which provide air gaps in a portion of the magnetic path around the central conductor 22 thus .causing the greater portion of 'the magnetic flux to flcwthrough the element 2D" at a greater distance from the conductor 22. In Fig. 3d, the hub portion 2l" of the translating element 20 is positioned at a distance from the inner conductor 22 of the transmission line thus to increase the length of the path of lowest magnetic reluctance aroundI the inner conductor.

It will be understood that a translating element having` any of the configurations of Figs. 3a-3d may extend longitudinally the full length of the transmission line or may simply be relatively short insulating spacers asr desired.

It was previously mentioned that an electromagnetic-wave translating element embodying the invention has the same characteristic impedance as free space but a wave-signal propagation velocity less than that of free space. It will thus be apparent that the translating element of the invention has utility where itisf desired that a wave-signal propagation path have an effective electrical length greater than its physical length. Fig. 4, which represents an application of this nature, illustrates a coaxial transmission line 33, 34 having a cylindrical electromagnetic-wave translating element 35 supported on the inner conductor 34 thereof. The element 35 isformed of a llm miogeneous mixture of dielectric and magnetic materials. To maintain uniformity of impedance along the transmission line, it can be shown that the radial thickness :c of the element 35 is given by the relation:

where n=the effective magnetic permeability of the material of element 35 llcv=the effective dielectric constant of the material of element 35 .The length of the velen'ient 35 is selected, of course,

to provide the desired effective increase of electricai length of the transmission line.

Figs. 5a and 5b illustrate top and side views of an electromagnetic-wave translating element 36 embodying the present invention and having the configuration of a spherical condensing lens. The element 36 is formed of laminations alternately of dielectric and magnetic materials similar to those of the element l0 of Fig. 1. In a thin spherical lens of this nature, or lens having a long focal length, parallel laminations provide a fair approximation of the desired lens action. However, it is preferable for the best lens action, especially in lens elements of short focal length, that the laminations have a Wedge-shaped cross section as indicated in Fig. 5b. The proper polarity or mode of wave-signal propagation through theelement 36 is indicated in Figs. 5a and 5b; namely, the magnetic field should be parallel to the laminations, as indicated by the arrow H of Fig. 5a, and the electric field should be normal to the laminations as indicated by the arrow E of Fig. 5b. It can be shown that the index of refraction n of the translating element 36 is given by the relation:

Where n'=the effective magnetic permeability of the element 36 The quantities of the dielectric and magnetic materials of the element 36 are proportioned, of course, to provide unity ratio of effective magnetic permeability to effective dielectric constant by use of Equation 1 or 1A so that the characteristic impedance of the element 36A is the same as that of free space. Hence, an electromagnetic wave propagated as a cylindrical beam of energy to the element 36 is concentrated by the latter to a focal point P without reflection of wave energy from either 4surface of the element 36. Conversely, electromagnetic-wave energy radiated fromy the point P is concentrated by the element 36 into a cylindrical beam ofwave-signal energy without reiiection vfrom the surfaces of the element 36. f

Figs. 6a and 6b are respectively a top view and a longitudinal sectional'view illustrating the use of translating elements embodying the present invention as 4cylindrical lens elements in a horn type of wave-signal radiator. The horn radiator 31, which has a configuration well known to those skilled in the art, is useful in effecting the radiation of a sharplyl concentrated beam of Awaveesigna-l energy. The horn illustrated is of rectangularv cross section `with a flaring end portion 38 and utilizes a dipole antenna Sil to initiate the propagationof electromagnetic waves therethrough. Translating elements lil, E2, 'i3 and i4, embodying Athefpresent invention, have lthe configuration of cylindrical condensing lens elements and are used to effect proper focusing of the electromagnetic-wave energy as it propagates down the horn 3l and into free space. `The orientation of. the dipole antenna 39 indicated in Figs. 6a and 6b provides the required mode of wave-signal propagation through the elements 4l, '42, 43 and 44; namely, With the magneitc eld of the electromagnetic wave parallel to the' laminations of the translating elementsv and with the electric field normal to the laminations thereof, as indicated'. respectively by the arrow H of Fig.. 6a. and' the arrow E of Fig. 6b. 'Ilhetranslating elements lll, 42, 43 and 54 each comprise dielectric and magnetic materials combined.' in quantities proportioned in the manner of the translating element iii ofv Fig. l so that the wave-signal propagation impedance is maintained uniform throughout the length of the horn 3l', which utilizes' air dielectric in the space between Vthe translating elements. As a consequence, no reflection of wave-signal energy occurs at anylens surface of the' translating elements thus to avoid the development. of any standing waves of voltage and current within the horn 31.. Such standing waves not only increase the wave-signal losses in the horn 3l, but impair the directional radiation characteristics desired ofthe latter.

Fig.,'7a represents a cross-sectional view of a rcctangular'wave guide 45 which. utilizes a laminated. ktranslating element 4B embodying the present invention to effect a change of direction of wave-signal Aenergy propagated along the wave guide. The wave guide 45 includesa first portion l) arranged at right angles to a second portion di' and includes a portion 48 which makes an obtuse angle 'with the portion Il?. The internal dimensions of the wave :guide 4l are proportional in well-known manner to effect wave-signal propagation therethrough. The use' oi" a right-angle turn, such, forV example, as that'between the wave-guide portions 50 and el, has heretofore been impractical'l for the reason that appreciable loss of wave-signal energy and distortion of vthe wave frontA has occurred Yat the turn due to severe reflection of wave-signal energy at that point. This. has also been; true in large part Where the bend inthe wave guidev was less than ak rightangle, for example, an obtuse anglesuch as that between the wave-guide portionsI 41 and 48. The use of a translating element 46, having the coniguration of a prism,v effects a Sil-degree change in the `direction of Wave-signal propagation and accomplishes this Without any reflection of wave-signal energy fromeither surface of the translating element 46. As a result, an electromagnetic wavepropagates: down the wave guide without loss of wave-signal energy and in the samer manner as though the wave guide were linear. The use of a Second laminated translatingi element i9` in accordance with the invention of prismatic configuration effects a similar change of direction of wave-signal propagation by an angle equal to that between the-portions 41 and 48'o-f the wave guide 45. The path of wavesignal propagation along the wave guide is thus that indicated. by the broken line.

When the mode of propagation of the electro-- magnetic wave is such that the magnetic field of the waveis paralleli to the median plane of the wave guide including the angled turn, the laminations of the translating element K5 are also parallel to the median? plane, as indicated in Fig.r 7a. However, when the mode of Wave-signal propagation is such that the electric field' of the wave signal is parallel to the median plane of the wave guide including the angled turn, as in Fig. 7b'. the laminations of theelement 46 are normal to the median plane as indicated in Fig. 7b. It will be understood that thel quantities of dielectric and magnetic materials of the translating elements 46', 4S and 49 are proportioned in the manner explained in connection with Figs. 1 and la to insure constant impedance to wave-signal propagation through the waveguide. The design of the-translating elementsI 46, 46 and 49 involve the same considerations that apply to thedesign of'fa light-refractive prism, the index of refraction being given by Equation 5 above.

It will be apparent from the above description ofthe invention that a high-frequency electromagnetic-wave translating element embodying the inventionV possesses high eiciency of wavesignal propagation particularly in that it causes minimum reflection of wave-signal energy from the boundary surfaces of the element in the path of wave-signal propagation. A translating element embodying the inventionk has the additional advantage that the velocity of wave-signal propagation through thel element may have any value within a range of valuesdetermined by the choice of the dielectric` and magnetic materials thereof. This feature is of importance where it is necessary to attain a desired value of increase of effective electrical length of a wave-signal propagation path for a given physical length thereof or to effect a desired value of index of refraction where it is desired that at least one surface of the translating element effect a change of direction of' a propagated wave signal.

While there have been described what are at present considered tob'e the preferred embodiments-of this invention, it will be obvious to those skilled the vart that various changes and modifications may be` made therein without departing from the invention, VandY it is, therefore, vaimed* in the appended claims to cover all such changes and modifications as Vfall within the true spirit and scopeY of the invention.

What is claimed is:

1. A high-frequency electromagnetic-wave translating element comprising dielectric and magnetic materials having perceptible boundaries and combined in quantities so proportioned with relation totheir dielectric constants and vmagnetic pei-'meabilitiesr asl to provide, lfor la predetermined mode of wave-signal propagation therethrough, an effectivedielectric constant anda substantially equal effective magnetic permeability.

2. An electromagnetic-wave translating element comprising dielectric and' magneticr mateterials having perceptible boundariesand having unequal dielectricv constants andmagnetic permeabilities but combined in quantities soY proportioned' with relation to their individual dielectrc constants and magneto permeabilities as to provide, for a predetermined mode of wave-signal propagation therethrough, an effective dielectric constantl and a substantially equal effective magnetic permeability.

3. An electromagnetic-wave translating el'ement comprising dielectric material having a predetermineddielectric' constant and unit magnetic magnetic permeabilities as to provide, for a pre-l determined mode of wave-signal propagation therethrough, an effective dielectric constant and a substantially equal eiiective magnetic permeability. y l

5. [in electromagnetic-wave translating element comprising dielectricmaterial and comminuted magnetic material held in solid suspension in at least a portionrof said dielectric material, the configuration of said element and the proportioned quantities of said materials being such as to. provide, for a predetermined mode of wave-signal propagation therethrough, an eiective dielectric constant; and a substantially equal effective magnetic permeability.

6. An electromagnetic-wave translating element comprising at least one layer of dielectric material land at least one contiguous layer of magnetic material combined in quantities so prO- poi-tioned with relation to their dielectric constants and magnetic permeablities as to provide, for a predetermined mode of wave-signal propagation therethrough,i an effective dielectric constant and a substantially equal effective magnetic permeability. I

'7. An electromagnetic-wave translating element comprising laminations alternatelyy of dielectric and magnetic materials having maximum lamination thickness much less than one radian length and combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal propagation therethrough, an effective dielectric constant and a substantially equal magnetic permeability.

8. An electromagnetic-wave translating element comprising at least two concentric cylindrical layers one of dielectric material and the other of magnetic material combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal propagation axially therethrough, an effective dielectric constant and a substantially equal effective magnetic permeability.

9. An electromagnetic-wave translating element, adapted to be used between inner and outer concentric conductive surfaces capable of supporting wave-signal propagation therebetween, comprising at least two concentric layers for surrounding said inner conductive surface one of said layers being of dielectric material and the other of magnetic material with said materials combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide between said surfaces, for a predetermined mode of wave-signal propagation axially therealong, an effective dielectric 14 constant and a substantially equal effective magnetic permeability.

l0. An electromagnetic-wave translating element, adaptedxto be used between spaced concentric conductive surfaces capable of supporting wave-signal propagation therebetween, comprising concentric cylindrical laminations for surrounding the inner of said conductive surfaces and alternately of dielectric and magnetic maw terials combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide between said surfaces, for a predetermined mode of wavesignal propagation axially therealong, an effective dielectric constant and a substantially equal effective magnetic permeability.

11.`An electromagnetic-wave translating element, adapted to be used between opposing electromagnetic-wave propagating surfaces having a predetermined spacing therebetween, comprising dielectric and magnetic materials having perceptible boundaries and combined in quantities so proportioned vwith relation to their dielectric constants and magnetic permeabilities as to provide between said opposing electromagnetic-Wave propagating surfaces, for a predetermined mode of wave-signal propagation through said element, an effective dielectric constant and a substantiallyequal effective magnetic permeability.

12. An electromagnetic-wave translating ele- 'inent, comprising dielectric and magnetic inaterials having perceptible boundaries and cornbinedvin quantities so proportioned with relation to their dielectric constants and magnetic permeabilities and having such configuration of said element in a cross section normal to the direction of wave-signal Vpropagation therethrough as to provide, for said direction of wavesignal propagation and for a predetermined mode ofy propagation therethrough, an effective dielectric constant and a substantially equal effective magnetic permeability.

13. An electromagnetic-wave translating element, adapted to be used between opposing electromagnetic-wave propagating surfaces having a predetermined spacing therebetween, comprising dielectric and magnetic materials having perceptible boundaries and combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode of wave-signal propagation therethrough and for an elementary unit volume of said combined materials, a predetermined dielectric constant and a smaller magnetic permeability, said element having such configuration in a cross section normal to the direction of wave-signal propagation therethrough as to provide between said surfaces an effective dielectric constant and a substantially equal effective magnetic permeability.

14. An electromagnetic-wave translating element, adapted to be used between spaced concentric conductive surfaces capable of supporting wave-signal propagation therebetween, comprising dielectric and magnetic materials combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide a predetermined dielectric constant and a smaller predetermined magnetic permeability, said element being conditioned to be positioned between said surfaces in contiguous relation to portions thereof and arranged to provide a closed magnetic path around the inner one of said surfaces and to provide radial paths between said surfaces of such length asm-src- :e 'and cross-sectional area transverse the direction of wave-signal propagation through said* elefment that there exists, for a predetermined mode of propagation through said element, an eiective dielectric constant and a substantially equal effective magnetic permeability.

1-5. An electromagnetic-wave translating' element, adapted to be used between concentricconductive surfaces capable of supporting wave- Signal propagation therebetween, comprising vdielectric and magnetic materials combined in quantities so proportioned with relation gto their dielectric constants and magnetic permeabilities as to provide a predetermined dielectric consta-nt and a predetermined magnetic permeability, said element having a rst portion forenclosingv the inner one of said surfaces and other portionsv radiating from said iirst portion to the` outer one of said surfaces, the radialthickness of said first portion of said element being so proportioned with vrelation to the length and cross-sectional areas of said other portions normal to the direction of wave-signal propagation through said element that there exists, for a predetern'rinedv mode of wave-signal propagation through said element, an effective dielectric constant and a substantially yequal eiectivemagnetic permeability.

16. An electromagnetic-wave translating element, adapted to be used between spaced concentric conductive surfaces capable of lsupporting wave-signal propagation therebetween, comprising dielectric and magnetic materials having predetermined dielectricconstants and magnetic errneabilities, said element having at least onev hub portion for surrounding the inner onefof said conductive surfaces and radial fin portionsy for extending from said hub portion to atleast the outer one of said conductive surfaces, the `orua-ntities of' such dielectric and magnetic materials i I6 tric constant and a substantially equal eective magnetic permeability;

1'7.. `An electromagnetic-wave translating element comprising dielectric and magnetic materials combined in quantities so proportioned with relation to their dielectric constants and magnetic'permeabilities as to provide, for a predetermined mode of Wave-signal propagation therethrough, an eective dielectric constant and a substantialli7 equal eiiective magnetic permeability, .the boundary surfaces of said element in the path of wave-signal propagation being dis posed in dierent planes and having such configurations as to enable said element to refract said wave signal to change the direction of wavesignal propagation from one side of said element to the other.

18. An electromagnetic-wave translating element comprising dielectric and magnetic materials combined in quantities so proportioned with relation to their dielectric constants and magnetic permeabilities as to provide, for a predetermined mode vof Wave-signal propagation therethrough, an eiective dielectric constant and a substantially equal eiective magnetic permeability, the'bou-ndaryl surfaces of said element in the path oi-"wave-signal propagation having such unequalourvatures as to modify the concentrationrof .electromagnetic energy along said path.

HAROLD A. WHEELER.

yREFERENCES CITED The following references are of record in the nle ofv this patent:

UNITED STATES PATENTS Tawney Feb. l, 1945 

